Method of measuring the energy of three-phase alternating-current circuits.



,,No. 7l7,496. Patented Dec. 30, I902.

F. CONRAD.

.METHOD OF MEASURING THE ENERGY RF THREE PHASE ALTERNATING CURRENTCIRCUITS.

(Application filed Tan. 6, 1902.)

(Ila Model.)

Rig. 2.

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UNITED STATES PATENT FFICE.

FRANK CONRAD, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION O PENNSYLVANIA.

METHOD OF MEASURING THE ENERGY F THREE-PHASE ALTERNATlNG-CURRENTCIRCUITS.

$PEGIFIGATION forming part of Letters Patent No. 717,496, dated December30, 1902.

Original application filed February 14, 1901, Serial No. 47,349. Dividedand this application filed January 6, 1902. $erial No. 88,601. (Nomodel.)

To all whom it may concern: as to measure the entire energy of such cir-Be it known that I,FRANK CONRAD, a citizen cuit. of the United States,residing at Wilkinsburg, My invention consists of a method. of comin thecounty of Allegheny and State of Pennbining the voltages and currents ofthree- 5 sylvania, have invented a new and useful Imphase circuits toattain the above-mentioned provement in Methods of Measuring theEnresults; and it is immaterial to the invention ergy of Three-PhaseAlternating-Current Cirwhat type or kind of wattmeter be employed cuits,of which the following is a specificaand whether it be provided withmeans for tion, this application being a division of an indicating,registering, or recording the en- 10 application filed by me February14, 1901, Seergy measured by it.

rial No. 47,349. Referring particularly to Fig. 1 of the draw- Myinvention relates to alternating-current ings, 1, 2, and 3 aretransformers the primary systems of electrical distribution andparticuwindings of Which are connected in delta to larly to methods ofmeasuring the energy of a threephase generator 4. The secondary 15 suchsystems. windings of the transformers 1, 2, and 3 are The object of myinvention is to provide a also connected in delta to a distributing ormethod whereby the energy of three-phase transmission circuit 5, 6, and7. In order to circuits may be accurately measured by a measure theoutput of the transformers 1, 2, two-phase wattmeter or by twosingle-phase and 3, I may employ a wattmeter of any suit- 2o Wattmeters.able construction. As an example of a suit In power installations it isoften found necable instrument, I have shown diagrammatessary to measurethe output of three transically a wattmeter 8, like that illustrated informers which are connected in delta to a Fig. 5 of Patent No. 608,842,granted to H. P. three-phase circuit or the energy of three cir- Davisand myself, August 8, 1898, in which 25 cuits which are otherwiseinterconnected in the armatures90f twoinstruments are mountsuch mannerthat the voltage of any one of ed upon a vertical shaft or spindle 10. Asethem is equal to the resultant voltage of the ries field-winding 11and a shunt field-windother two. It is obvious that such energy ing 12are employed in conjunction with each may be measured by means ofindependent armature,and suitable phase-adjusting means 0 single phasewattmeters respectively conand friction-compensating means may also benected to the several circuits, the readings of employed, as set forthin the patent above rethe three meters being added together; but ferredto, if desired. inasmuch as it is always desirable to sim- Whileconvenience and compactness of arplify apparatus so far as may bepracticable rangement may make it desirable to embody 35 Withoutimpairing the efficiency it will obthe above-mentioned mechanism in asingle viously be advantageous to measure the eninstrument, it would befeasible to employ ergy of three interconnected circuits by means twoindependent instruments, since the only of a single instrument. I havetherefore deinterdependence which exists in the strucvised the methodillustrated in the accompature, as shown, resides in the mounting of theo nying drawings, in whicharmatures upon a single shaft or spindle andFigure 1 is a diagram of a portion of a the employment of a singleregistering dethree-phase system embodying three transvice 13. formersthe primaries of which are connect- For the reason just stated themeasuring ed to the source of current in delta and the apparatus shownmay for convenience be re- 5 secondaries of which are connected in thegarded as comprising either one or two insame manner to a three-phasedistributingstruments, and I therefore desire it to be uncircuit and inwhich a two-phase wattmeter derstood that references hereinafter made inis so connected to the transformer secondathe specification or theclaims either to memries as to accurately measure the output. Fig. bersof one instrument or to two instruments I00 50 2 is a diagram of athree-phase four-wire cirare not to be construed as excluding eithercuit and a two-phase wattmeter so connected of the arrangementsmentioned.

In utilizing the instrument 8 in accordance with my present invention Iconnect the shunt-windings of the upper and lower members of thewattmeter respectively to the secondary windings of transformers 14 and15, the primary windings of which are respectively connected across thecircuits 1 1 and 3 3 Inductive resistance-coils 16 may be included incircuit between each of the shuntwindings 12 and the secondary of thecorresponding transformer 14 or 15 for the purpose of retarding thephase of the currents in the shunt-windings in the usual manner. It willbe understood that the shunt-coils 12 of the wattmeter may be connecteddirectly to the conductors 1 1 3 and 3 in cases where the voltages ofthe circuits are suitable for the said coils. The series coils of theupper and lower members of the instrument 8 are respectively suppliedwith currents propor tional to those of the circuits 1 1 and 3 3 bymeans of series transformers 17 and 18, the primaries of suchtransformers being respectively included in conductors l and 3 To theextent above described the connections are those used in connection witha polyphase wattmeter employed for measuring the output of a two-phasecircuit, the upper member of the instrument measuring the output of thetransformer 1 and the lower member measuring the output of thetransformer 3.

In order to measure the output of transformer 2, I provide a seriestransformer 19, the primary of which is included in the conductor 2,leading from the secondary of the transformer 2, and make connections asfollows: The terminals of the secondary winding 20 of the transformer 19are respectively connected by means of conductors 21 and 22 to oneterminal of the series coil 11 of the upper member and to thecorresponding terminal of the series coil 11 of the lower member of theinstrument 8. The other terminals of the coils 11 are connected togetherby means of conductors 23 and 2 1. It will be seen, therefore, that thecurrent from the secondary 20 of series transformer 19 passes throughthe two windings 11 in series, and consequently that the current in theseries winding of the upper member of the instrument 8 will be theresultant of the currents delivered by transfromers l and 2, While thecurrentin coil 11 of the lower member of the instrument will be theresultant of the currents delivered by the transformers 2 and 3.

As has already been pointed out, the electromotive force impressed uponthe shuntwinding of the upper member will be that of the transformer 1,while the electromotive force impressed upon the shunt-winding of thelower member will be that of the transformer 3. Since the voltage of anyone of three transformers connected in delta in a three-phase circuit isequal to the resultant of the voltages of the other two transformers, itfollows that the voltage of transformer 2 is equal to the resultantvoltage of transformers 1 and 3. It follows, therefore, that if twowattmeter readings were taken in which one should be the product of thecurrent from transformer 2 by the voltage from transformer 1 and theother should be the product of the current from transformer 2 by thevoltage from transformer 3 the sum of these readings would be equal tothe energy supplied by transformer 2. Since the current from thetransformer 2 is thus accurately measured twicethat is, once with thevoltage from the transformer l in the upper member and once with thevoltage from transformer 3'in the lower member of the instrument 8--itfollows that the energy delivered by the transformer 2 as Well as thatdelivered by transformers 1 and 3 will be properly measured. in theinstrument 8.

It will of course be understood that the primary windings of the seriestransformers may be included in either of the legs of the respectivecircuits.

Referring now particularly to Fig. 2 of the drawings, 25 is athree-phase generator that supplies energy to a four-wire three-phasecircuit 26,27,28, and 29 either directly or through suitabletransformers, as is usual in the art.

As indicated in the drawings,the conductors 26, 27, 28, and 29 supplyelectriclights but I do not intend to thereby exclude other forms oftranslating devices. The wattmeter 8, employed for measuring the energyof circuits 26, 27, 28, and 29, may be of the same construction as thatalready described and is, in fact, shown of the same construction asthat illustrated in Fig. 1. The description heretofore given of theinstrument may be therefore read in connection with this figure, thereference-n umerals being the same in both figures.

As in the case of energy supplied by three transformers connected indelta to threephase circuits, it has heretofore been the practice to usethree single-phase meters for measuring the output of four-wirethree-phase circuits, such as are illustrated in Fig. 2. In order toutilize a single two-phase instrument or two independent single-phaseinstruments, and thereby simplify the apparatus and reduce the cost, Imake connections as follows: The shunt-winding 12 of the upper member ofthe instrument is connected across circuit 26 29 and the shunt-winding12 of the lower member of the instrument is connected across circuit 2829. If the voltages of the circuits 26 29 and 28 29 are too high for theshuntcoils of the instrument, transformers may be employed, as indicatedin Fig. 1. The series winding 11 of the upper member of the instrumenthas its terminals respectively connected tothe terminals of thesecondary winding of a series transformer 31, the primary of which isincluded in conductor 26. In a similar manner the terminals of theseries winding of the lower member of the instrument are connected tothe terminals of connections thus far described are such as to measurethe energy of circuits 26 29 and 28 29. In order to also measure theenergy of circuit 27 29,1 include the primary of the series transformer33 in conductor 27 and connect one terminal of the secondary winding toone terminal of the secondary transformer 32 and the other terminal ofsaid winding to one terminal of the'secondary winding of transformer 31.I also connect the opposite terminals of the secondaries of transformers31 and 32 together by means of a conductor 34. With this arrangement ofcircuits it will be seen that the current from transformer 33, startingwith the terminal connected to one terminal of the secondary oftransformer 32, will pass through the series winding of the lower memberof the instrument 8, and by way of the conductor 34 through the serieswinding of the upper member of the instrument 8, and by the connectionsshown back to the other terminal of the secondary of transformer 33. Asin the system illustrated in Fig. 1, the voltage of each of the circuitshere shown is equal to the resultant of the voltages of the other twocircuits, and it will therefore appear from the description given inconnection with theapparatus and circuits illustrated in Fig. 1 that theinstrument 8 will accurately measure the energy of all three of thecircuits 26 29, 27 29, and 28 29. It will be understood, in connectionwith this form of the invention, that the primary winding of each of theseries transformers may be connected with either leg of thecorresponding circuit.

It is of course to be understood that the wattmeters hereinbeforedescribed are so designed and calibrated as to measure the true energyof the circuits to which they are con nected and that the actualpropelling forces which are applied to the movable members of theinstruments are dependent upon the phase angles between the respectivecurrents and the corresponding voltages, and consequently that any givenpropelling force equals the product of current multiplied by voltage andalso by the cosine of the phase angle between current and correspondingvoltage.

Such other modifications as may be made without materially affecting themode of operation and result I regard as within my invention and desireto cover by my claims. The connections whereby a two-phase Wattmeter ortwo single-phase wattmeters may be employed for measuring the energy ofthree circuits may be utilized. in connection with any system Where thevoltage of any one of the three connected circuits is equal to theresultant of the other two, and my invention is intended to cover themeasurement of the energy of all of such circuits.

I claim as my invention 1. The method of measuring the energy of threeinterconnected, alternating-current circuits which consists inseparately measuring the products of the currents and voltages of two ofthe circuits and atthe same time measuring the product of the current ofthe third circuit by the voltages of the said two circuits.

2. The method of measuring the energy of three interconnected,alternating-current circuits which consists in simultaneously subjectingthe movable member of an energymeasuring instrument to theindependentlyapplied propelling force of the products of the currentsand voltages of two of the circuits and the cosines of the phase anglesbetween the respective currents and the corresponding voltages and tothe propelling force of the product of the current of the third circuitby the voltages of the other two circuits and the cosines of the phaseangles between said current and the respective voltages.

3. The method of measuring the energy of three interconnected,alternating-currentcircuits which consists in independently imparting tothe movable member of an energymeasuring instrument the propelling forceof the products of the currents and voltages of two of the circuits andthe cosines of the phase angles between the respective currents and thecorresponding voltages and that of the product of the current of thethird circuit by the voltages of the other two circuits and the cosinesof the phase angles between said current and the respective voltages.

In testimony whereof I have hereunto subscribed my name this, 31st dayof December, 1901.

- FRANK CONRAD.

Witnesses:

O. 0. OWENS, JAMES B. YOUNG.

ICO

